1. Field of the Invention
The present invention relates generally to methods of manufacturing a diamond heat sink, and more particularly, to a method of manufacturing a diamond heat sink produced by metallizing a diamond surface formed by means of vapor phase synthesization.
2. Description of the Background Art
In association with developments in today's high information-intensive society, the performance of semiconductor devices such as a semiconductor laser diode and an IMPATT diode used for transmitting information has been remarkably improved. In order to further improve the performance of these semiconductor devices, thermal energy generated by these devices should be radiated or dissipated to restrict the temperature increase of the devices. The heat sink is used for such heat radiation. The material known as the best for the heat sink was type II a natural diamond.
Meanwhile, heat sinks have been produced using synthetic diamond, and such heat sinks exhibit high thermal conductivity comparable to type II a natural diamond, with a smaller variation in quality, and therefore have stable heat radiation performance, contributing to improvements in the performance and reliability of various semiconductor devices and prolonging the life of the devices.
The present invention relates to a method of manufacturing a diamond heat sink produced by metallizing a surface of such synthetic diamond, in other words diamond synthesized by means of vapor phase synthesization.
Five specific examples of a conventional method of manufacturing a diamond heat sink will be now described. In a first conventional example, a diamond polycrystal body is cut into pieces of a prescribed shape by a diamond saw. The diamond pieces cut into a prescribed shape are arranged close to each other and metallized. Metallizing the upper and lower surfaces completes the diamond heat sink.
In a second conventional example, a diamond polycrystal body is cut into pieces of a prescribed shape by a diamond saw. After metallizing the entire surface, end faces of the pieces are ground using a grind stone to leave the metal film only at the upper and lower surfaces and the diamond heat sink is completed.
In a third example, a diamond polycrystal body having its surface metallized is cut into pieces of a prescribed shape by a diamond saw to complete a diamond heat sink.
In a fourth example, as disclosed by Japanese Patent Laying-Open No. 5-114677, and corresponding U.S. Pat. No. 5,294,381 after metallizing the surface of a diamond polycrystal body, grooves are made in the diamond using a laser, followed by mechanical separation to complete a diamond heat sink.
In a fifth conventional example, diamond is cut into pieces of a prescribed shape by a laser. The conductive portion of each end face is removed by means of an oxidation treatment, and then the pieces are arranged close to each other for metallization. Thus metallizing the upper and lower surfaces completes a diamond heat sink.
Diamond heat sinks have been conventionally manufactured as described above.
In a cutting method using a diamond saw, however, a diamond polycrystal body cannot be highly precisely cut or a large margin is necessary for cutting.
A margin for grinding should be further taken into account for grinding. A method using a laser provides precise cutting, but a conductive layer (graphite layer) is sometimes formed at a cut surface due to graphitization and other damages caused by the laser. An oxidation treatment to remove the conductive layer is therefore necessary. In that case, after a diamond polycrystal body is cut into pieces of a prescribed shape, metallization should be performed. However, after cutting a diamond polycrystal body into pieces of a prescribed shape, metallization with a complicated pattern using photolithography or the like cannot be performed.
Furthermore, in the above-described method of making grooves using a laser after metallization, a chip portion is formed at an end surface in the final mechanical separation process.